Generally, the present invention relates to ovens used in the production of fiber cord or cords or webs. More specifically, the present invention relates to air seals used to contain gases within an oxidation oven used in the production of carbon fibers.
Oxidation ovens are used in the process of making multifilament carbon fiber tows from polyacrylonitrile (PAN) precursor fibers. An example process and apparatus for making such fibers is described in U.S. Pat. No. 4,100,004 to Moss et al., incorporated herein by reference. A byproduct of the oxidation of PAN fibers is hydrogen-cyanide gas or HCN. HCN is hazardous to workers in the carbon fiber production facility and is preferably contained within the oxidation ovens until it can be properly disposed of through an exhaust system. During the production process, the fibers enter and exit the oxidation ovens many times through openings in the ends of the ovens. In the past, mechanical seals have been used to block air flow out of the oven to prevent worker exposure to HCN. However, the mechanical seals are not as effective as would be desired in blocking air flow in or out of the ovens. Accordingly, air hoods positioned over the ends of the ovens and in other work areas have been used to remove gases escaping from the oven from the production facility.
A second concern with the prior art ovens is that cold ambient air enters the oven through the openings. This leads to the non-uniform treatment of the fibers within the oven. The result is a carbon fiber product of substandard quality. Uniform treatment of the fibers is essential to maintaining product quality.
The present invention overcomes these disadvantages by providing an oven having an oven chamber adapted to treat a product being passed therethrough. The oven chamber has sides and ends. At least one of the ends has a first opening and a second opening. The product passes through the openings for treatment in the oven chamber. The first opening is disposed above the second opening. The oven is also provided with a first nozzle adjacent the first opening and a second nozzle adjacent the second opening. Each nozzle is effective for discharging air from an air flow pathway into the oven chamber and forming an air curtain at the opening to which it is adjacent. A diffuser is provided immediately downstream of each of the first and second nozzles, with each diffuser cooperating with the associated first or second nozzle to form an ejector or inductor therewith.